IrfanView - IrfanView ... one of the most popular viewers worldwide.
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
Adobe Acrobat DC - Make your job easier with Adobe Acrobat DC, the trusted PDF creator. Use Acrobat to convert, edit and sign PDF files at your desk or on the go.
FastStone Image Viewer - FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
Wondershare PDFelement - All-in-one PDF editor